Frozen hamburgers, chicken patties, sausage patties, and other disk-like food products typically are prepared by a manufacturer on one piece of equipment and then fed into a freezer. After leaving the freezer, they are screened by a metal detector, which causes contaminated patties to be ejected, and then conveyed to a stacker. Because the stacks formed by some stackers can vary in height, and because the number of stacks formed simultaneously by a stacker may be greater than the number of stacks that will fit in a case, the finished stacks are often manually removed from the stacker and loaded into cases. This manual loading step is labor-intensive, and, due to the presence of a human element, highly variable.
One known prior art patty stacking machine is disclosed in U.S. Pat. No. 6,052,969, assigned to the assignee of the present application, which is hereby incorporated by reference. That machine includes a conveyor for moving patties in a first direction and dropping them into helical coil. The patties fall between the loops of the coil, and as the coil is rotated, new loops are presented for receiving additional patties. The rotation of the coil advances the patties into a holder, and when the holder is filled, a mechanical jaw grips the stack and moves it to a packing station from which it is loaded into a packing machine. This machine serves its intended purpose adequately, but suffers from various problems such as being bulky. In addition, if patties are not accurately aligned with loops of the coil, they may hit the coil instead of falling between the loops which leads to stacks of varying heights and to product waste.
To maximize efficiency, it is preferable to have the entire process of stacking and packing patties automated, and to do so in a manner that allows for continuous production and that minimizes the likelihood of product jams. Furthermore, it is desirable that a patty stacking machine can easily be retrofitted to the end of a patty processing production line and that the machine be sufficiently compact so as not to interfere with other existing parts of the processing machinery.